py: Overhaul and simplify printf/pfenv mechanism.

Previous to this patch the printing mechanism was a bit of a tangled
mess.  This patch attempts to consolidate printing into one interface.

All (non-debug) printing now uses the mp_print* family of functions,
mainly mp_printf.  All these functions take an mp_print_t structure as
their first argument, and this structure defines the printing backend
through the "print_strn" function of said structure.

Printing from the uPy core can reach the platform-defined print code via
two paths: either through mp_sys_stdout_obj (defined pert port) in
conjunction with mp_stream_write; or through the mp_plat_print structure
which uses the MP_PLAT_PRINT_STRN macro to define how string are printed
on the platform.  The former is only used when MICROPY_PY_IO is defined.

With this new scheme printing is generally more efficient (less layers
to go through, less arguments to pass), and, given an mp_print_t*
structure, one can call mp_print_str for efficiency instead of
mp_printf("%s", ...).  Code size is also reduced by around 200 bytes on
Thumb2 archs.

1 files changed, 2 insertions, 0 deletions

diff --git a/py/misc.h b/py/misc.h
index f920d52a1..2c00b6880 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -147,6 +147,8 @@ typedef struct _vstr_t {
 void vstr_init(vstr_t *vstr, size_t alloc);
 void vstr_init_len(vstr_t *vstr, size_t len);
 void vstr_init_fixed_buf(vstr_t *vstr, size_t alloc, char *buf);
+struct _mp_print_t;
+void vstr_init_print(vstr_t *vstr, size_t alloc, struct _mp_print_t *print);
 void vstr_clear(vstr_t *vstr);
 vstr_t *vstr_new(void);
 vstr_t *vstr_new_size(size_t alloc);